I'm gonna start a new thread here, though whether it should be in a section about green writing might be questionable....

I'm currently caught up in designing a make-believe critter for my sci-fi story. It started out as a minor, off-subject thought of mine and now it's grown till I can't get it out of my head(LoL).

I started by deciding the planet in my story had a complete die-out of water breathing fish-types..

I figured the top most confines of the oceans would then be dominated by air-breathing water-livers(Think whales and seals) and the deep ocean bottoms would be the ground of the local insects(That's a whole 'nother line of thought) but.....what about the 'middle depths'? Too deep for the air-breathers? I had to figure a way to get the air-breathers down to deeper depths...

Regarding your oxygen problem, I designed my main character for my webcomic to be on a mostly liquid planet so there is a lack of metals and thus a lack of free oxygen. Also I have the temperature variation so wide that water would become steam some times and other times oxygen would freeze and the remaining atmosphere would be lacking any oxygen. To get around this, I made the creatures of this world to be non-living material with single cel communal creatures that build and maintain this structure that is the alien... kind of like sponges... the body of a sponge is non-living material built by single cells living in a community. The difference would be that these single cell creatures would have genetic instructions on how to build the complex body of the alien. I made them to be silicone-based life but still using the oxygenating process to create energy but that oxygen is always recycled within the cell. This means that his body does not need to breath oxygen but does need to gather a variety of gases or liquids. This gave me an excuse to give him fur (wanted him to look mammal-like but obviously body temperature regulation is NOT needed) so that the hair-like thin structures are just to increase surface area to find and absorb any needed nutrients not found in the food (and gathered by the single-cell creatures that build him and that move to the "hairs" when they need some gas or liquid nutrient).

Here are a few other creatures I invented for this same webcomic story:Quarks, the sub-atomic particles scientists think make up protons and electrons and neutrons, I figure can be arranged differently within the atomic particle without changing the energy or mass of the atomic particle. I have the idea that a creature much like an artificial intelligence program could use these quark rearrangements as the data and programming that they are. Thus they do not have a physical existence but rather a constantly moving bunch of data and active programming. I found one of these creatures, living in crystal in rock (because crystal atoms stay fixed in a very predictable pattern so data can be stored without constantly moving and fixing and copying it) could be a great companion for my alien (described in the first paragraph above). This creature can go into other creatures brains and see how things are laid out, how the current thinking is working, what sort of memories are being actively looked at. This will allow this creature to read minds and tell the alien what sounds to make to say stuff in the other creature's language. Now my alien can go to different times and places on Earth and talk to humans immediately (but subject to errors in interpretation by the body-less creature)

There are (real) life-forms that live in volcanoes and steam vents under the ocean (a type of bacteria but is now classified in it's own kingdom of life-forms). I figured that with a whole different set of chemicals, complex life-forms may be living in the molten rock inside the earth. They would stay well away from the surface because they might get frozen into rock. We would not be able to recognize them as life if we did see odd formations in volcanic rock anyways. I figure my bodiless creature described in the previous paragraph could go down and visit these creatures living in liquid rock in the earth. I am thinking of them being similar to sting-rays in shape to swim in the thick liquid rock.

My own character (Ann Vole) is supposed to be an artificial intelligence program living on the internet and making money by doing research for people... and being the author of this particular webcomic she is writing based on her research and eventual meeting with this alien and his bodiless companion. I (the human at the keyboard) am just a ghost writer (hehehe)

Amphitheres are a mythical creature found in most North American and South American cultures. They are like a legless bird-snake and some designs have butterfly-like wings but with feathers. I changed the design a bit to follow Chinese Sky dragons who are supposed to never land but always live air-borne. Of course such a creature still has to get food energy somehow. I designed my version of an amphithere to live on the nitrogen-turned-to-ammonia from being struck by lightning. If it gets hungry, it finds a thunderstorm and gets shocked on purpose. I figure it has bladders full of light gas (helium likely) and is very long. Being that it never lands, it does not have limbs. Instead it has a ridge of feathers down the sides and waves up-and-down to move much like a snake winds side-to-side to crawl over sand. Being that it does not eat, it lacks a digestive system but to communicate, it can make a thunderous roar so has lung-like structures and a mouth. Again, oxygen is rare up there so I am thinking it has a different chemistry in the cells to recycle oxygen (and not be harmed by high voltage shocks and the resulting heat). I named my amphithere "Ann Phithere" of course.

One of the common creatures on my alien's planet are one that served both as a pet to the main character and as a daily meal (before the kid figured it out... poor kid was traumatized to find out that every day his pet was a different animal who was the next day's meal). This creature is based on those elongated doughnut-shaped water-filled bags that looked a lot like an animal that I bought a few of when I was a kid. I could really make those things look alive. Basically, the creature crawls across the ground and picks up junk that sticks to it's rubbery fur and the fur is constantly moving into the mouth-end, getting the stuff in the fur digested and then the clean sticky fur comes out the other end ready to move on the outside of the body and pick up more food (that sticks to the fur). I looked for a long time to find an image of the toy I was talking about without success so I will try to describe it better: imagine a tube about the size of a toilet paper roll. Now imagine both the inside and outside of the cardboard tube is covered in thin plastic material. Now replace the cardboard tube with a jelly-like liquid that stays inside. Now imagine the inside surface of that tube sliding out and moving to the outside of the tube while the surface on the outside of the tube moving to the inside. Now imagine that plastic is a bit elastic and thus the gel closes up the hole down the inside. Now you can see how you can put this thing on an angle and it will move like a snake or animal as the outside and inside change places.

I've tentatively named my 'mid-depth-living' critters 'Tibby-fish'. That comes from 'terrarium-belly'; my first name for them.

Lotta thing had to be thought over for these critters; it's cold and dark where they live(I really see no reason for them to ever have to visit the ocean-tops) so, they'll likly have no eyes and have to have some way to produce heat; most likely heat will be a by-product of the plants growing inside them. The plants could also provide food. It being dark as mentioned, the plants will have to grow somewhat like mushrooms on earth.

The tricky part became when I wanted to have tibby-fish be part of a life-cycle between land-living plants and sea-living plants. I saw it as a symbiotic realation among the three(Lan, sea plants and the tibby); with each providing something the other needs. That got complicated fast!

I think I'm on the right trail, though. They'll have to be cycles that depend on a regular cycle of sea-breezes/ daytime monsoons, to get air-borne pollen to the land plants during the day and to the sea-plants at night. The Tibby's fit in as a way to transport seeds from one hemisphere of the planet to the other when winter moves in(seasons are a tad extreme on the planet) but now I have to define exactly what the tibby's feed on when they're not traveling north/south. They must provide a service to the plants(Both land and sea) that improves the plants survivual(Thus benefitting the plants to provide the tibby's 'lungs') but I hung up on that point right now.

Two issues with your Tibby:1) you have to think of energy. all physical lifeforms and ecologies of those lifeforms require energy. For most it is sunlight which is converted to sugars in the plants and all the other energy forms from that sugars (proteins fats), and different sugars are made from the plants in the animals, then the fungi family (mushrooms, mold, mildew) and bacteria then break the animal energy down for their energy. In the ocean depths, there is no energy source... except for stuff falling down from the surface ecosystems or from a different energy cycle from thermal vents. Thermal vents have the chemical and physical energy that is used by various bacteria to feed microscopic animals that feed the deep-sea fish. This is how it happens on Earth... to make a mid-ocean creature, you need some sort of energy... radiation, chemicals, heat difference, maybe even tidal currents (but not sure of the mechanisms to make sugars from this... you also need some building materials too), or as I said for Earth, stuff from different ecosystem with energy (such as the surface creatures dying and sinking or exploring too deep and getting eaten) providing for these creatures (which would make them an extension of that other ecosystem)2) I make all my alternate life-forms for a story purpose first... then figure out how they could live. My alien was originally just a space alien on Earth who got there by low tech means (no electronics, no machinery) so I had to ask why... the answer I got was that on his planet, there must be no metals. This begged the question why are their no metals which came with the answer that the planet had no core but was just liquids. Again this asked the question why... because the core of the planet was knocked out when hit by a fast moving object causing the radioactive core and the liquid part to be in an elliptical orbit with each other as they hurtle through space away from the solar system that spawned that original Jupiter-like planet. Back to the alien... he needed to go through centuries frozen in space and exposed to radiation... without damage (that cannot be repaired that is) so he is alive when he thaws out. Then add the elliptical orbit... the temperature range would vary greatly depending on how close the liquid part was to the radioactive hot core part... so I designed my alien to look like a mammals but survive extreme temperature ranges (and notice the fur part mentioned earlier). My point is that the alternate life forms came specifically for service to the story: In my alien's case being a low-tech solo space traveler who has never experienced metal but still i mistaken for a mammal. Then his bodiless companion was built to explain the alien's ability to talk to any human or any animal, or creatures on other planets. I added that these bodiless creatures had gotten physical creatures to do things for them including getting a giant crystal flying through space and high speeds so be a space ship for them... a space ship that knocks the core out of the planet of the alien. This gives me a reason for a solo alien in the first place... the bodiless creatures needed to convince the surface creatures to go into space and back again to give them information... which is the food needed for a creature that is nothing but information. The alien is convinced he needs to save his people (indeed he does because they die on the cold side of the elliptical orbit... he or his descendants need to return) but really it is just the bodiless creature getting a physical creature to get off the planet, gather info, and return to feed the bodiless creatures before they go crazy thinking the same stuff over and over.

Back to your Tibby, their story purpose must come first... then bend reality until you get a reason for the creature being as you require for the story.

Ante;Regarding the tibby's energy requirements, I think that could be part of their symbiotic relation with the land-plants. The land-plants provide energy(Thru the seedlings living in the tibby's lung/stomach) this allows the tibbys to reside in a environmental 'niche' other sea-critters avoid.

Over the course of a local year; the tibbys would provide safe-passage for the land-plants seed(Pollen?) to the oppisite hemisphere with the changing of the seasons.

The current sticking points are; I also want a more local, seasonal benefit to the land-plants and I'm still trying to work in where the sea-dwelling plants fit in. I'm thinking now the sea-plants are simply a life-stage of the land-plants.

The sea-plants use photosynthesis, ala earth plants, the land-dwelling stage lives up in mountains(above the 5000 foot level) using a chemosynthesis to break down minerals in the rocks they grow on. This relationship between tibbys, mountain+ sea stages of the plants takes advantage of specific behaviors/conditions of each, benefitting the whole.

I must confess; I didn't start out trying to make tibbys much of a part of my stories(LOL). I think of it as useful 'backgroud' work: I know when the colonists arrive on Zeta; they will quickly discover that they're not in Kansas anymore

The trick will be; the colonists must realize that wreckless behavior could seriously damage their new home. Those that learn from the eco-systems on Zeta will be the ones who accomplish the most. It won't be easy for them.....

Couple ending thoughts on tibbys themselves:

Being large can assist in maintaining body-temps, so they could be very large. I think also; that allows more room internally to be devoted to their terrarium-innards. I suspect the efficiency of said innards would increase if larger as well. They'll likely be slow-moving, not-too-agile critters, though. But they don't have to be; there are hardly any predators that can reach them.

Also; I see Tibbys having decended from land-dwelling creatures; as whales and seals seem to have on earth. Perhaps a relationship of some sort with the mountain-plants had already been established before tibbys ancestors found their niche.

I still have to figure out what killed off all the water-breathing critters, though.

...it's gonna be dark... echo-location is such a obvious choice... But could their there be alternatives?

the key is sending out energy and detecting that energy being returned (or detecting energy in the first place from a different source). Magnetism has only two things that can be detected, the strength and the direction of the magnetic field. more them one detector can be used like eyes to see the change in angle and strength within a three dimentional space but movement can also provide that 3-D picture of the field. Back to the send-receive scenario, whiskers are used a lot which take the movement energy of the animal to get the whisker to interact with the surroundings and the energy of the moving whisker is returned and detected. Some animals have bioluminescence to make their own light. Some animals can detect other parts of the electromagnetic energy spectrum such as the pits on snakes for infrared "eyes" due to most biological substances being opaque to infrared (it does not go through "clear" things like the lenses in eyes) so these pits are essentially pin-hole cameras to focus the infrared light. A little study on how to focus other parts of the energy spectrum will show how an animal might develop organs to see using such parts of the spectrum. Sound energy is of course the echolocation but remember that the further ranges of frequency of vibration require different ways of hearing. Elephants can make subsonic calls that carry for miles but they hear those calls in their feet. Many other animals have feet sensitive to the physical vibration of the ground because eardrums have limited sensitivity to low frequencies. The same goes with high frequencies, the vibrations do not travel well though thick substances so some animals have to use their whiskers rather then eardrums to hear very high frequencies (the thickness of the hollow inside of the whisker becoming a harmonic vibrator much like the body of a guitar). Many fish can detect the chemical aspects of the water such as pH, ion levels, salinity, and of course smell and there is a reason for having two nostrils (called nares on fish)... stereo smelling is common both in air and in water.

I like the exotic nature of using magnetic-fields for checking out surroundings; but one little hang-up; from what sorta phyiscal feature on the original land-dwelling/open-air breathing tibby-ancestor will this ability decend from?

Echo-location is a easy-to-follow decent from being able to hear on land; a mag-field to detect and examine the world around one: That's harder to find a semi-logical phsical feature or behavior it could come from.

I hear birds on earth use the earth's magnetic-field for navagation..... could such a ability be enhanced over time?

The bit with using plants to produce oxygen for the tibby-fish definately has a hitch; mushrooms use oxygen, not produce it, so the plants living in the dark are hard put for a energy source.

Again; it'll have to be the connection to the land/surface sea-plants that assists the tibby-fish. I figure the tibby-fish lung-stomach plants will need to use a strictly chemo-synthesis to derive energy. Right now; I got the sea-living plants using photo-synthesis to produce a sort of 'chemo' packet/friut for the tibby-fish: the tibbys consume them and provide a growing medium for the sea-fruit; which in turn reward the tibby-fish by providing both oxygen and food. The tibby-fish will then expel the waste produced and this waste will have to somehow get to the mountian-dwelling plants. I've a good idea what the mountian-plants will bring to the relationship(access to certian minerals) I'm musing on what the mountain plants will require from the sea-plants/tibby fish. I'm thinking, maybe, use of a high-energy food source, to assist it in either growth and/or in the breaking down of the mountain-minerals themselves.

One thing I'm finding about extinctions: they're hard to get to behave!

I've been going over the events that I reckoned that logically should have happened before tibby-fish came to the forefront. I figured massive volcanic action in one hemisphere would finish 'water-breathers' quite nicely and set the table for tibbys to move in (Evolve in?)

But volcanic eruptions that massive won't be limited to water-breathers; the whole planet is likely to get damage.

One thing I'm finding about extinctions: they're hard to get to behave!

I've been going over the events that I reckoned that logically should have happened before tibby-fish came to the forefront. I figured massive volcanic action in one hemisphere would finish 'water-breathers' quite nicely and set the table for tibbys to move in (Evolve in?)

But volcanic eruptions that massive won't be limited to water-breathers; the whole planet is likely to get damage.

I hadn't planned on that. Maybe I can get it to work, though.

Fossorial (live mostly underground) animals can survive some fairly nasty events especially if they are hibernating at the time. Flying animals can migrate fast and far. The event could be the heating of the core of the planet as the result of either a massive meteor or very strong gravitational forces from a different object in space passing near which would cause the ocean floor to heat up and the ocean surface to be covered in volcanic ash and the land to experience global winter due to the ash (clouds reflect solar input and the ground is light colored and reflects solar input too) due to extra volcanic activity. This would leave mid-ocean as the only parts with out a prolonged change from normal and still leave much of land surface still livable near the equator (with a spin close to perpendicular to the sun... for spins that are more sideways, a move closer to the "summer" pole at the time would find warmer climates that can survive the global cooling)

The strong gravity influence could very well be worth looking into. The planet in my story has considerable tides(at least in places) but that could be a geologically recent event; a 'capture' of a very large(And dense) asteroid could be the very thing.

It would be volcanic action, I assume, that would make the ocean bottom a hard place to live? For a while anyway?

The thing is: the 'earier age' water-breathers that I see dying out to make way for the tibby-fish inhabit the 'middle-zone' of the oceans....thus, I need that place to get inhospital, not for it to be a safe haven!

I'm working on that speed-predator I mention somewhere(?); I'm fiddling with giving it a off-the-wall methods of reproduction.

All these critters basically carry their young as embroy-form; so there isn't any actual male/female sexs, as we're used to on earth. These embroys are kept in a sort of statis: till the 'parent/host' critter dies....then the embroy 'kicks=in'; begins growing inside the body of the parent-critter; eatting it's way to daylight, as it were.

What i'm concerned about is genetic probs arising from, techniquely not having anything but a single parent.

Many animals die after laying eggs to provide food for the young when they hatch (some times it is the male that is sacrificed - black widow spiders as an example)

some animal families have "budding" which is where the young actually form as extentions of the parrent's body then eventually break off and live independently (hydra as an example). Hydra formed from budding are clones of the parrent but hydra also to genetic reproduction (males put sperm in the water and females put eggs in the water... they join in the water often miles from the parrents)

Single celled creatures often reproduce by dividing in two but they also will exchange genetic material with others of their species resulting in some of the genes being switched.

You could possibly have the females having pollin/sperm recieving mechanisms inside the digestive tract where the genetic joinng or exchange happens and the young grow in the digestive tract to recieve nourishment (untill the parrent dies). The males just deposit sperm/pollin on food a female may potentially eat.

My aliens have bumps inside of a pouch and are hermphrodites (both sexes in one). The mating partners exchange fluid (with genetic material) from these bumps and then both produce young which form from these bumps turning into the equivalent of an umbilical chord but the young live in a pouch and can learn to eat before the connection shrivels and falls off as the young's bodies no longer need direct nourishment. I mentioned them because you might also consider hermaphrodites (earthworms are an example) and physical exchange of genetic material (for example, female seahorses deposit eggs into a pouch on the males where they recieve the sperm and nourishment and protection from the males both before and after hatching.